Responsa su Deuteronomio 18:13

And if so, there is no prohibition here, only the positive commandment to “be whole-hearted” [with the Lord your God, Deut. 18:13] as it is written, and it seems from his words that he is not proclaiming a real prohibition. And I say, with all due respect [to the Rosh], he did not read the words of the Rambam carefully enough, as he wrote in chapter 11 in Idol Worshippers, “It is forbidden to do magic or to ask a magician, rather we inflict the lashes of rebellion upon the asker, and the magician who actually does this act [of magic] is lashed” etc. (Mishneh Torah, Avodat Kochavim, chapter 11)

And if so, you can see that he explicitly declares that both of them are prohibited [by Torah], but because here [in the case of the question being asked] there is no [actual] act, we do inflict merely rabbinic lashes upon him [as opposed to biblical], as he wrote in that same chapter about the asker of a medium, and what is written in that same chapter that they are in the general prohibition because of “wholehearted you shall be” (Deut. 18:13), this is specifically for those who believe in them. On this he says that he is among fools and idiots, and the Torah warns against this nonsense and those who believe in it and think that it’s the truth, as he wrote explicitly, “And only on those who believe,” wrote Rambam in that same chapter, [in the case that] his work or his profession in a fixed way is an astrologer of the heavens, indeed he is lashed.